1. Field of the Invention
The present invention relates to a thin film magnetic head of inductive type, a production method thereof, and magnetic recording apparatus.
2. Description of the Related Art
Recently, the recording density of a hard disc apparatus has been remarkably increased. Since the 1990 year, the recording density has been increased by about 60% every year. In order to increase the recording density of a hard disc apparatus, it is necessary to reduce the magnetic head track width so as to increase the recording track density. Furthermore, in order to increase the recording density, it is also important to increase the recording bit density. For increasing the recording bit density, it is necessary to increase the recording medium having a high coercive force Hc requires an inductive magnetic recording head having a high recording efficiency. Moreover, in order to effectively detect a signal from a small recording bit, it is necessary to use an MR reproduction head. Accordingly, there is a great expectation on a high density recording realized by using an MR head in combination with an inductive recording head, i.e., a thin film magnetic head of the MR-inductive composite type.
FIG. 15 and FIG. 16 show a conventional thin film magnetic head of the MR-inductive composite type. FIG. 16 is plan view of the entire configuration and FIG. 15 is a cross sectional view about the XVxe2x80x94XV line in FIG. 16.
The conventional thin film magnetic head 70 includes a lower shield layer 74, a read gap layer 80, a lower pole layer 82 serving also as an upper shield layer; and a write gap layer 84 formed in this order on an insulation substrate (not depicted). The thin film magnetic head 70 also includes a magneto-sensitive element inserted into the read gap layer and facing the ABS (air bearing surface) 76. The thin film magnetic head 70 further includes: the a first filling material layer 86 formed on the write gap layer 84 excluding the vicinity of the ABS 76; a coil pattern layer 88; and a second filling material layer 90 formed in this order. The thin film magnetic head 70 further includes a recording pole layer 92 formed on the write gap layer 84 and the first filling material layer 86 as well as on the second filling material layer 90.
The lower pole layer 82 serves as a lower pole layer of the inductive recording head as well as an upper shield layer for increasing the reproduction resolution. The MR magneto-sensitive element 78 detects a signal magnetic field from a magnetic storage medium (not depicted) facing the ABS 76. The write gap layer 84 has a thickness as a gap of the inductive recording head. The first filling material layer 86 serves as an insulation fundament of the coil pattern layer 86. The second filling material layer 90 dissolves the convex and concave configuration of the coil pattern layer 88.
Explanation will now be given on the recording operation of the thin film magnetic head 70. A magnetic flux generated when electric current is applied to the coil pattern layer 88 flows from a pole window 94 at the center of the coil pattern layer 88 through the recording pole 92 having a small magnetic reluctance (by 10 to 100 times compared to the air) to return to the pole window 94. On the other hand, the recording pole and the lower pole layer 82 are connected to each other via a space provided by the write gap layer. Accordingly, a portion of the magnetic field in the write gap layer 84 leaks to the ABS 76, generating a recording magnetic field.
FIG. 17 and FIG. 18 shows a part of the thin film magnetic head 70 enlarged partially. FIG. 18 is a partial plan view, and FIG. 17 is a cross sectional view about the line XVIIxe2x80x94XVII in FIG. 18 Explanation will now given, referring to these figures.
Firstly, in this Specification the terms xe2x80x9cwidthxe2x80x9d and xe2x80x9clengthxe2x80x9d are defined as follows. The width is in a direction vertical to the thickness direction of the write gap layer 84 and parallel to the ABS 76. The length is in a direction vertical to the ABS 76.
The recording pole 92 can be divided into a tip portion 921, a flare portion 92, and a yoke portion 923 in this order from the side of the ABS 76. The flare portion 922 reduces its width continuously from the yoke portion 923 toward the tip portion 921. The tip portion 921 extends with a constant width W from the ABS 76 to reach the flare portion 922.
Referring to FIG. 17 and 18, it is assumed that the tip portion 921 has tip length L. The tip length L is determined by a mask pattern used when performing frame plating of the recording pole layer 92. Moreover, a gap depth D is assumed to be a distance between the ABS 76 and the tip of the first of the first filling material layer. That is, the depth D is a portion of the write gap layer sandwiched only by the recording pole layer and the lower pole layer. The recording track width is determined by the tip width W of the recording pole layer 92 and is almost equal to the tip width W. In order to obtain a high recording density, it is necessary to realize the recording pole layer 92 having a tip width W as small as possible.
As shown in FIG. 18, the relationship between the tip length L and the gap depth D is conventionally L greater than D. Accordingly, the tip portion 921 is partially located on a stepped portion of the first filling material layer 86. On the other hand, the photo-resist pattern used for forming the tip portion 921 deteriorates the dimension accuracy because the light is reflected by the stepped portion during exposure. Accordingly, in order to form the tip width W at the ABS 76 with a high dimensional accuracy, the flare portion 922 reflecting a large amount of light should be located at a large distance from the ABS 76.
The magnetic flux which has passed through the yoke portion 923 is converged at the flare portion 922 and further converted at the narrow tip portion 921. When the tip length L is large, a considerable leak is caused at a narrow portion of a high magnetic reluctance such as the tip portion 921. This decreases the magnetic flux supply to the tip portion 921. This, in turn, decreases the magnetic field at the write gap layer 84 at the ABS 76. Accordingly, in order to reduce the magnetic reluctance at the tip portion 921 so as to obtain a sufficient recording magnetic field, it is necessary to make the tip length L as much as possible.
However, if the tip length L is decreased, the flare portion 922 is formed at a position nearer to the ABS 76. Accordingly, if the tip length L is reduced, as has been described above, the light reflection from the stepped portion deteriorates the pattern formation accuracy at the tip portion 921.
Thus, the accurate formation of the tip reduction of the magnetic reluctance of the tip portion 921 so as to obtain a sufficient recording magnetic field.
It is therefore an object of the present invention to provide a thin film magnetic head, a production method thereof, and a magnetic recording apparatus, wherein the tip width can be formed with a high accuracy without increasing the magnetic reluctance at the tip portion. The present invention provides a thin film magnetic head comprising a write gap layer formed on a lower pole layer; a first filling material layer, a coil pattern layer, a second filling material layer which are successively formed in this order on the write gap layer excluding the vicinity of the ABS; and a recording pole layer formed on the write gap layer at least in the vicinity of the ABS. The recording pole layer is divided into a tip portion, a wide rear portion, a flare portion, and a yoke portion in this order viewed from the ABS. The tip portion and the wide rear portion are provided on the write gap layer. The wide rear portion has a greater width than the tip portion when the width is determined as vertical to the film thickness direction of the write gap layer and parallel to the ABS.
The present invention is characterized by the wide rear portion provided between the tip portion and the flare portion. The wide rear portion is provided together with the tip portion on the flat write gap layer. Accordingly, no light is reflected by the wide rear portion to the tip portion during exposure. Moreover, the wide rear portion has a greater width than the tip portion, which mitigates increase of the magnetic reluctance. Accordingly, it is possible to provide the flare portion reflecting a large quantity of light, far from the ABS so as to improve the pattern accuracy, while suppressing increase of the magnetic reluctance.
In the thin film magnetic head claimed in claims 3 to 10, some of the components of the thin film magnetic head of claim 1 are defined precisely.